Experimental study on seismic behavior of circular steel tube confined reinforced self-stressing steel slag concrete columns

Low-cycle reversed loading test were conducted on 10 circular steel tube confined reinforced self-stressing steel slag concrete columns and four circular steel tube confined reinforced steel slag concrete (SSC) columns, to investigate the influence of the shear span ratio, axial compression ratio, diameter-thickness ratio and expansion ratio of SSC on the seismic performance of the specimens. The results indicated that the crushing of core SSC at the bottom of columns and yielding of longitudinal reinforcement dominated the specimens damage. Fine circumferential tensile cracks without development trend along the height direction appeared at the non-shear plane of the columns. The hysteretic curves were generally full, which denoted that the specimens had good seismic behavior. With the increase of the axial compression ratio, diameter-thickness ratio, or decrease of the shear span ratio, the strength degradation was more severe and the ductility reduced. The stiffness degradation rate was accelerated with the increase of the axial compression ratio, or reduction of the expansion ratio of SSC or shear span ratio. In addition, as the axial compression ratio or expansion ratio of SSC raised, or the shear span ratio reduced, the ductility of the specimens decreased and the growth of the energy dissipation coefficient was accelerated.